Recent years have seen progress in the development and practical implementation of display devices (hereafter referred to as organic EL display devices) using organic EL elements. Generally, an organic EL display device includes (i) a display unit having, arranged in a matrix, pixel circuits each having an organic EL element, and (ii) a control circuit for controlling the display unit.
With regard to the pixel circuit used in organic EL display devices known as an active-matrix type, there is proposed a driving method and a circuit configuration made up of a small number of circuit components and having various functions for making organic EL elements emit light more precisely and stably (for example, Patent Literature (PTL) 1).
FIG. 8 is a circuit diagram showing a conventional pixel circuit 90 disclosed in PTL 1. The pixel circuit 90 includes a drive transistor TD, switching transistors T1 and T2, a capacitive element Cs, and an organic EL element EL.
In the pixel circuit 90, a control circuit not shown in the figure supplies: selection signals Vsea and Vseb, via selection lines Lsea and Lseb; a detecting voltage Vmeas and a gray scale voltage Vdata, via a data line Ld; and a power source voltage via a power source line La and a common electrode Ec.
According to the pixel circuit 90, first, the threshold voltage of the drive transistor TD which changes over time is identified by measuring the current flowing in the drive transistor TD according to the application of the detecting voltage Vmeas, and the identified threshold voltage is stored in the control circuit not shown in the figure. Then, by causing the organic EL element EL to emit light using the gray scale voltage Vdata that has been corrected based on the stored threshold voltage, it is possible to cause light emission at a precise and stable luminance regardless of the change over time of the threshold voltage of the drive transistor TD.